Fölsz Orsolya, Trouche Stéphanie, Croset Vincent
Department of Biosciences, Durham University, Durham, United Kingdom.
MSc in Neuroscience Programme, University of Oxford, Oxford, United Kingdom.
Front Neurosci. 2023 Feb 15;17:1128623. doi: 10.3389/fnins.2023.1128623. eCollection 2023.
Although most neurons are generated embryonically, neurogenesis is maintained at low rates in specific brain areas throughout adulthood, including the dentate gyrus of the mammalian hippocampus. Episodic-like memories encoded in the hippocampus require the dentate gyrus to decorrelate similar experiences by generating distinct neuronal representations from overlapping inputs (pattern separation). Adult-born neurons integrating into the dentate gyrus circuit compete with resident mature cells for neuronal inputs and outputs, and recruit inhibitory circuits to limit hippocampal activity. They display transient hyperexcitability and hyperplasticity during maturation, making them more likely to be recruited by any given experience. Behavioral evidence suggests that adult-born neurons support pattern separation in the rodent dentate gyrus during encoding, and they have been proposed to provide a temporal stamp to memories encoded in close succession. The constant addition of neurons gradually degrades old connections, promoting generalization and ultimately forgetting of remote memories in the hippocampus. This makes space for new memories, preventing saturation and interference. Overall, a small population of adult-born neurons appears to make a unique contribution to hippocampal information encoding and removal. Although several inconsistencies regarding the functional relevance of neurogenesis remain, in this review we argue that immature neurons confer a unique form of transience on the dentate gyrus that complements synaptic plasticity to help animals flexibly adapt to changing environments.
尽管大多数神经元在胚胎期就已生成，但在成年后的特定脑区，包括哺乳动物海马体的齿状回，神经发生仍以较低速率持续进行。海马体中编码的情景样记忆需要齿状回通过从重叠输入中生成不同的神经元表征（模式分离）来使相似经历去相关。整合到齿状回回路中的成年新生神经元与驻留的成熟细胞竞争神经元的输入和输出，并募集抑制性回路来限制海马体的活动。它们在成熟过程中表现出短暂的过度兴奋性和可塑性增加，这使得它们更有可能被任何给定的经历所募集。行为学证据表明，成年新生神经元在编码过程中支持啮齿动物齿状回中的模式分离，并且有人提出它们为连续编码的记忆提供时间标记。神经元的不断添加会逐渐破坏旧的连接，促进海马体中远程记忆的泛化并最终导致遗忘。这为新记忆腾出空间，防止饱和和干扰。总体而言，一小部分成年新生神经元似乎对海马体信息的编码和清除做出了独特贡献。尽管关于神经发生的功能相关性仍存在一些不一致之处，但在本综述中，我们认为未成熟神经元赋予齿状回一种独特的短暂性形式，它补充了突触可塑性，以帮助动物灵活适应不断变化的环境。
